* Ancient Origins: Sandals with a thong-like strap between the toes existed in ancient Egypt and other cultures. These were precursors to flip-flops.
* Modern Evolution: Rubber flip-flops, similar to the ones we wear today, were likely developed in the early 20th century, probably in Japan or the United States, but there's no clear documentation.
* Popularization: The popularity of flip-flops soared in the 1960s and 1970s with the rise of beach culture and casual wear.
* Branding: Companies like Havaianas and Reef started producing and branding flip-flops, which further increased their popularity.
So, while a specific year of invention is difficult to pinpoint, the development of flip-flops was a gradual process influenced by different cultures and innovations.